Combustion apparatus

ABSTRACT

An exhaust portion is connected to a lower peripheral edge of a secondary heat exchanger case, has an exhaust vent configured to exhaust combustion gas which has passed through the secondary heat exchanger case, and has a bottom surface including a first face parallel to the lower peripheral edge. A drainage water discharge port is configured to discharge drainage water from the first face of the bottom surface. The drainage water discharge port is provided, to avoid a region overlapping with the secondary heat exchanger case from a point of view as seen in an up-down direction, in an exhaust path from the secondary heat exchanger case toward the exhaust vent.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a combustion apparatus.

Description of the Background Art

An inverse combustion apparatus having an exhaust vent for exhausting combustion gas and a discharge port for discharging drainage water is disclosed, for example, in Japanese Patent Laying-Open Nos. 2000-292010 and 2006-275367.

In a construction described in Japanese Patent Laying-Open No. 2000-292010, an exhaust pipe is inclined entirely directly under a can body which accommodates a sub-heat exchanger.

In a construction described in Japanese Patent Laying-Open No. 2006-275367, a bottom casing which accommodates a secondary heat exchange portion is provided with a drainage water discharge port.

SUMMARY OF THE INVENTION

When considering internal layout and cost for reducing the size of an inverse combustion apparatus, it is desirable to have a small exhaust pipe. In the construction of Japanese Patent Laying-Open No. 2000-292010, however, it is difficult to reduce the thickness of the exhaust pipe because the exhaust pipe is inclined entirely directly under the can body, and it is thus difficult to achieve size reduction.

In the construction of Japanese Patent Laying-Open No. 2006-275367, a muffler extends upward from the bottom casing which accommodates the secondary heat exchange portion toward an exhaust vent. Thus, a large amount of combustion gas is generated that moves toward the exhaust vent without passing through the secondary heat exchange portion. The efficiency of heat exchange at the secondary heat exchange portion is therefore low.

The present invention was made in view of the problem above, and an object thereof is to provide a combustion apparatus which has high heat exchange efficiency, which can be readily reduced in size, and which is able to efficiently discharge drainage water.

A combustion apparatus according to the present invention includes a combustion portion, a heat exchanger of latent heat recovery type, a heat exchanger case, an exhaust portion, and a drainage water discharge port. The combustion portion is configured to generate combustion gas. The heat exchanger of latent heat recovery type is configured to exchange heat with combustion gas generated by the combustion portion. The heat exchanger case has an internal space and is configured to accommodate the heat exchanger in the internal space. The exhaust portion is connected to a peripheral edge which is one of an upper peripheral edge and a lower peripheral edge of the heat exchanger case, has an exhaust vent configured to exhaust combustion gas which has passed through the heat exchanger case, and has a bottom surface including a first face parallel to the peripheral edge. The drainage water discharge port is configured to discharge drainage water from the first face of the bottom surface. The drainage water discharge port is provided, to avoid a region overlapping with the heat exchanger case from a point of view as seen in an up-down direction, in an exhaust path from the heat exchanger case toward the exhaust vent.

According to the combustion apparatus in the present invention, the bottom surface of the exhaust portion has the first face parallel to the peripheral edge of the heat exchanger case. Thus, the thickness of the exhaust portion in the up-down direction can be reduced as compared to an example where the bottom surface of the exhaust portion includes only an inclined face relative to the peripheral edge. The size reduction in the up-down direction is thus facilitated.

The exhaust portion is connected to the peripheral edge of the heat exchanger case, and includes the exhaust vent configured to exhaust the combustion gas which has passed through the heat exchanger case. Thus, most of the combustion gas passes through the heat exchanger of latent heat recovery type. The efficiency of heat exchange at the heat exchanger of latent heat recovery type can thus be improved.

Drainage water which has fallen to the bottom surface of the exhaust portion from the inside of the heat exchanger case is pushed by a flow of the combustion gas to move along the bottom surface from directly under the heat exchanger case toward the exhaust vent. In the present invention, the drainage water discharge port is provided, to avoid the region overlapping with the heat exchanger case from the point of view as seen in the up-down direction, in the exhaust path from the heat exchanger case toward the exhaust vent. Thus, the drainage water which has moved along the flow of the combustion gas above can be efficiently discharged through the drainage water discharge port.

In the combustion apparatus, the exhaust portion has a rising portion rising from the bottom surface. The drainage water discharge port is arranged at a corner formed by the bottom surface and the rising portion.

At the corner formed by the bottom surface and the rising portion, a flow velocity of the combustion gas decreases. The drainage water thus stays at the corner. By providing the drainage water discharge port at this corner, therefore, the drainage water staying at the corner can be effectively discharged through the drainage water discharge port.

In the combustion apparatus, the rising portion is composed of an outer wall of the exhaust portion.

Accordingly, the drainage water staying at a corner between the outer wall and the bottom surface of the exhaust portion can be discharged through the drainage water discharge port.

In the combustion apparatus, the rising portion is a plate member arranged in the exhaust path.

At a corner formed by the plate member rising from the bottom surface in the exhaust path other than the outer wall and the bottom surface, too, a flow velocity of the combustion gas decreases, causing the drainage water to stay at the corner. By providing the drainage water discharge port at this corner, therefore, the drainage water staying at the corner formed by the plate member and the bottom surface can be effectively discharged through the drainage water discharge port.

In the combustion apparatus, the bottom surface of the exhaust portion includes a second face inclined relative to the peripheral edge of the heat exchanger case to have a down grade toward the first face.

This facilitates guiding of the drainage water which has fallen to the second face to the first face by the inclination of the second face. Discharge of the drainage water from the first face through the drainage water discharge port is thus further facilitated.

In the combustion apparatus, the drainage water discharge port is provided in a sidewall of the exhaust portion and opens laterally.

Accordingly, the space below the exhaust portion can be effectively eliminated, allowing for a further reduction in the dimension of the combustion apparatus in the up-down direction.

In the combustion apparatus, the first face is provided with a guiding inclined face having a down grade toward the drainage water discharge port.

Discharge of the drainage water on the first face through the drainage water discharge port via the guiding inclined face is thus further facilitated.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a construction of a combustion apparatus in one embodiment.

FIG. 2 is an exploded perspective view showing a construction of part of an exhaust portion of the combustion apparatus shown in FIG. 1 and a heat exchanger case.

FIG. 3 is a partial breakaway perspective view showing a construction of an exhaust collection and guide member in the combustion apparatus shown in FIG. 1.

FIG. 4 is a plan view of the exhaust collection and guide member shown in FIG. 3.

FIG. 5 is a schematic cross-sectional view taken along the line V-V in FIG. 4.

FIG. 6 is a schematic cross-sectional view taken along the line VI-VI in FIG. 4.

FIG. 7 is a schematic cross-sectional view taken along the line VII-VII in FIG. 4.

FIG. 8 is cross-sectional view showing a construction of an exhaust collection and guide member in a comparative example.

FIG. 9 is a plan view showing a construction of a first variation of the exhaust collection and guide member.

FIG. 10 is a schematic cross-sectional view taken along the line X-X in FIG. 9.

FIG. 11 is a plan view showing a construction of a second variation of the exhaust collection and guide member.

FIG. 12 schematically shows a construction of a combustion apparatus in another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below in detail with reference to the drawings.

It should be noted that the same or corresponding components are denoted by the same characters in the specification and drawings, and redundant description thereof is not repeated. In addition, constructions may be omitted or simplified in the drawings for the sake of illustration. Further, the embodiment and each variation may be at least partially combined together in an arbitrary manner.

<Construction of Combustion Apparatus 10>

As shown in FIG. 1, a combustion apparatus 10 in the present embodiment is a combustion apparatus of inverse combustion type. Combustion apparatus 10 includes an exhaust portion 1, a secondary heat exchanger 11, a secondary heat exchanger case 12, a primary heat exchanger 13, a primary heat exchanger case 14, a combustion portion 15, a fan 16, a drainage water tank 17, and a housing 20.

Exhaust portion 1, secondary heat exchanger 11, secondary heat exchanger case 12, primary heat exchanger 13, primary heat exchanger case 14, combustion portion 15, fan 16 and drainage water tank 17 are accommodated in housing 20.

Fan 16 serves to supply mixed gas of fuel gas and fuel air to combustion portion 15. An air supply pipe 16 a is connected to fan 16. Air supply pipe 16 a extends to the outside of housing 20 in combustion apparatus 10.

Combustion portion 15 serves to burn the mixed gas to generate combustion gas serving as gas for heating. Combustion portion 15 is a combustion device of inverse combustion type which supplies combustion gas downward. The combustion gas exchanges heat with water in each of primary heat exchanger 13 and secondary heat exchanger 11.

Primary heat exchanger case 14 and secondary heat exchanger case 12 are connected to combustion portion 15 so that the combustion gas sequentially passes through primary heat exchanger 13 and secondary heat exchanger 11. Primary heat exchanger case 14 is attached below combustion portion 15, and secondary heat exchanger case 12 is attached below primary heat exchanger case 14.

Secondary heat exchanger case 12 has an upper peripheral edge 12 b and a lower peripheral edge 12 a. Upper peripheral edge 12 b of secondary heat exchanger case 12 is connected to a lower peripheral edge of primary heat exchanger case 14. Secondary heat exchanger case 12 and primary heat exchanger case 14 form a can body. Secondary heat exchanger case 12 and primary heat exchanger case 14 are made of a metal material including copper or aluminum, for example.

Primary heat exchanger case 14 and secondary heat exchanger case 12 each have an internal space. Primary heat exchanger 13 of sensible heat recovery type is accommodated in the internal space of primary heat exchanger case 14. Primary heat exchanger 13 is a fin-and-tube type heat exchanger, for example. Secondary heat exchanger 11 of latent heat recovery type is accommodated in the internal space of secondary heat exchanger case 12. Secondary heat exchanger 11 is a fin-and-tube type heat exchanger, for example. Secondary heat exchanger 11 may be a plate type heat exchanger.

Exhaust portion 1 is connected to lower peripheral edge 12 a of secondary heat exchanger case 12. Exhaust portion 1 includes an exhaust collection and guide member 2, an exhaust duct 3, and an exhaust vent 4. Exhaust portion 1 serves to exhaust combustion gas which has passed through secondary heat exchanger case 12 to the outside of housing 20 in combustion apparatus 10.

Exhaust portion 1 is made of a material different from that for secondary heat exchanger case 12 and primary heat exchanger case 14. Exhaust portion 1 is made of resin, for example.

Drainage water tank 17 serves to store drainage water generated at secondary heat exchanger 11 or primary heat exchanger 13. Drainage water tank 17 is connected to exhaust portion 1. Specifically, drainage water tank 17 is connected through a pipe 18 to a drainage water discharge port 2 aa in exhaust collection and guide member 2.

In combustion apparatus 10 shown in FIG. 1, when a temperature of hot water introduced to primary heat exchanger 13 of sensible heat recovery type is low, or when an amount of heating by combustion portion 15 is small, water vapors of the combustion gas condense in primary heat exchanger 13, generating condensed water (drainage water). Drainage water is generated also in secondary heat exchanger 11 of latent heat recovery type. Such drainage water flows through exhaust collection and guide member 2 of exhaust portion 1 to be drained to drainage water tank 17.

<Construction of Exhaust Portion 1>

As shown in FIG. 1, exhaust collection and guide member 2 is connected to lower peripheral edge 12 a of secondary heat exchanger case 12 by a bolt, for example. Exhaust duct 3 is connected to exhaust collection and guide member 2. Exhaust duct 3 extends upward, for example, from exhaust collection and guide member 2. Exhaust vent 4 is connected to exhaust duct 3. Exhaust vent 4 extends upward, for example, from exhaust duct 3. The combustion gas which has passed through secondary heat exchanger case 12 is exhausted through exhaust collection and guide member 2, exhaust duct 3 and exhaust vent 4 to the outside of housing 20.

Exhaust portion 1 has a bottom surface 2 b. Bottom surface 2 b is a bottom surface of exhaust collection and guide member 2, and is a bottom surface in an exhaust path. Bottom surface 2 b is located below secondary heat exchanger case 12. Bottom surface 2 b has a first face 2 ba and a second face 2 bb.

First face 2 ba has a face parallel to lower peripheral edge 12 a of secondary heat exchanger case 12. First face 2 ba is a substantially horizontal face when combustion apparatus 10 is properly installed.

Second face 2 bb has a face inclined relative to lower peripheral edge 12 a of secondary heat exchanger case 12. Second face 2 bb is inclined by an angle θ, for example, relative to lower peripheral edge 12 a of secondary heat exchanger case 12.

As shown in FIGS. 2 and 3, bottom surface 2 b may have a third face 2 bc in addition to first face 2 ba and second face 2 bb. Third face 2 bc has, similarly to second face 2 bb, a face inclined relative to lower peripheral edge 12 a of secondary heat exchanger case 12.

Second face 2 bb and third face 2 bc are each connected to first face 2 ba. Second face 2 bb and third face 2 bc are also connected to each other.

As shown in FIG. 2, secondary heat exchanger case 12 and exhaust duct 3 are connected to an upper end portion of exhaust collection and guide member 2.

As shown in FIG. 4, first face 2 ba, second face 2 bb and third face 2 bc are each located in a region RA overlapping with secondary heat exchanger case 12 from a point of view as seen in an up-down direction (in plan view). The up-down direction as used herein refers to a direction in which exhaust collection and guide member 2 and secondary heat exchanger case 12 are stacked on each other, which is a point of view shown in FIG. 4.

Second face 2 bb is located only in region RA overlapping with secondary heat exchanger case 12, and is not located in a region RB overlapping with exhaust duct 3, from the point of view as seen in the up-down direction. In contrast, first face 2 ba and third face 2 bc are each located both in region RA overlapping with secondary heat exchanger case 12 and in region RB overlapping with exhaust duct 3, from the point of view as seen in the up-down direction. Region RB is a region where exhaust collection and guide member 2 and exhaust duct 3 are joined to each other.

Exhaust collection and guide member 2 has a sidewall 2 d and drainage water discharge port 2 aa. Sidewall 2 d of exhaust collection and guide member 2 surrounds bottom surface 2 b, and rises upward from bottom surface 2 b. Sidewall 2 d forms an outer wall of exhaust portion 1.

Drainage water discharge port 2 aa opens at sidewall 2 d and extends laterally. Drainage water discharge port 2 aa serves to discharge drainage water which has fallen to bottom surface 2 b of exhaust collection and guide member 2 to drainage water tank 17 (FIG. 1) from exhaust collection and guide member 2.

Drainage water discharge port 2 aa is provided, to avoid region RA overlapping with secondary heat exchanger case 12 from the point of view as seen in the up-down direction, in the exhaust path from region RA toward exhaust vent 4 (FIG. 1).

Drainage water discharge port 2 aa is provided in sidewall 2 d in region RB overlapping with exhaust duct 3 from the point of view as seen in the up-down direction. Drainage water discharge port 2 aa is also provided to be able to discharge drainage water from first face 2 ba of bottom surface 2 b.

Bottom surface 2 b further has a guiding inclined face 2 c. Guiding inclined face 2 c is provided in region RB overlapping with exhaust duct 3 from the point of view as seen in the up-down direction. Guiding inclined face 2 c is provided on first face 2 ba and third face 2 bc so as to reach drainage water discharge port 2 aa. Guiding inclined face 2 c extends linearly toward drainage water discharge port 2 aa.

As shown in FIG. 3, exhaust collection and guide member 2 has a bolt attachment portion 2 e and support portions 2 f. Bolt attachment portion 2 e and support portions 2 f each rise from bottom surface 2 b into the exhaust path. Bolt attachment portion 2 e is a portion into which a bolt (not shown) for fixing exhaust collection and guide member 2 to secondary heat exchanger case 12 is to be inserted. Support portions 2 f are portions for supporting an upper end portion 2 m (FIG. 2) with respect to bottom surface 2 b of exhaust collection and guide member 2.

As shown in FIG. 5, first face 2 ba is parallel to upper end portion 2 m of exhaust collection and guide member 2. Second face 2 bb is inclined to have a down grade toward a joining portion of first face 2 ba and second face 2 bb.

Guiding inclined face 2 c is recessed relative to first face 2 ba. Although not shown, guiding inclined face 2 c is also recessed relative to third face 2 bc. Guiding inclined face 2 c has an arc shape, for example, in cross section.

Drainage water discharge port 2 aa is provided at a corner formed by first face 2 ba and a rising portion rising from first face 2 ba. In the present embodiment, the rising portion rising from first face 2 ba is sidewall 2 d. Thus, drainage water discharge port 2 aa is provided at a corner formed by first face 2 ba and sidewall 2 d.

That drainage water discharge port 2 aa is provided at the corner includes not only the case in which drainage water discharge port 2 aa is provided in contact with the corner, but also the case in which drainage water discharge port 2 aa is provided while being laterally spaced apart from the corner by a predetermined dimension. This predetermined dimension refers to a dimension required based on constraints on integral formation of drainage water discharge port 2 aa and sidewall 2 d, which is several mm (not more than 1 cm), for example.

As shown in FIG. 6, third face 2 bc is inclined to have a down grade toward a joining portion of first face 2 ba and third face 2 bc.

As shown in FIG. 7, guiding inclined face 2 c is provided in region RB where exhaust collection and guide member 2 overlaps with exhaust duct 3 from the point of view as seen in the up-down direction. Guiding inclined face 2 c is provided across both first face 2 ba and third face 2 bc. Guiding inclined face 2 c is inclined to have a down grade until reaching drainage water discharge port 2 aa.

Effects of Present Embodiment

Effects of the present embodiment will now be described in comparison with a comparative example shown in FIG. 8.

In the comparative example shown in FIG. 8, drainage water discharge port 2 aa is located in region RA where exhaust collection and guide member 2 overlaps with secondary heat exchanger case 12 from the point of view as seen in the up-down direction. In this comparative example, combustion gas flows from a side of region RA where exhaust collection and guide member 2 overlaps with secondary heat exchanger case 12 to a side of region RB where exhaust collection and guide member 2 overlaps with exhaust duct 3, as indicated by an arrow in the figure.

Accordingly, drainage water DR1 which has fallen to bottom surface 2 b of exhaust collection and guide member 2 on a side opposite to the side of region RB with respect to drainage water discharge port 2 aa is pushed by a flow of the combustion gas to reach the drainage water discharge port. In contrast, drainage water DR2 which has fallen to bottom surface 2 b of exhaust collection and guide member 2 on the side of region RB with respect to drainage water discharge port 2 aa has difficulty in being pushed by the flow of the combustion gas to reach drainage water discharge port 2 aa.

In particular, when the quantity of airflow exhausted by fan 16 increases, or when the exhaust path in exhaust collection and guide member 2 decreases in area due to size reduction, a flow velocity of the combustion gas exhausted in the exhaust path above increases, making the problem above more pronounced.

In contrast, according to the present embodiment, as shown in FIG. 5, drainage water discharge port 2 aa is provided, to avoid region RA where exhaust collection and guide member 2 overlaps with secondary heat exchanger case 12 from the point of view as seen in the up-down direction, in the exhaust path from region RA toward exhaust vent 4 (FIG. 1). Thus, drainage water which has fallen to bottom surface 2 b of exhaust collection and guide member 2 from the inside of secondary heat exchanger case 12 can be pushed by the flow of the combustion gas to readily reach drainage water discharge port 2 aa. Accordingly, the drainage water can be efficiently discharged through drainage water discharge port 2 aa.

According to the present embodiment, as shown in FIG. 1, bottom surface 2 b of exhaust portion 1 has first face 2 ba parallel to lower peripheral edge 12 a of secondary heat exchanger case 12. Thus, the thickness of exhaust portion 1 in the up-down direction can be reduced as compared to an example where bottom surface 2 b of exhaust portion 1 includes only an inclined face relative to lower peripheral edge 12 a. The size reduction of combustion apparatus 10 in the up-down direction is thus facilitated.

According to the present embodiment, as shown in FIG. 1, exhaust portion 1 is provided separately from secondary heat exchanger case 12 which accommodates secondary heat exchanger 11. Exhaust portion 1 is connected to lower peripheral edge 12 a of secondary heat exchanger case 12, and is configured to exhaust the combustion gas which has passed through secondary heat exchanger case 12. Thus, most of the combustion gas is able to pass through secondary heat exchanger 11 of latent heat recovery type. The efficiency of heat exchange at secondary heat exchanger 11 of latent heat recovery type is thus improved.

According to the present embodiment, as shown in FIG. 5, drainage water discharge port 2 aa is arranged at the corner formed by bottom surface 2 b and the rising portion (sidewall 2 d) rising from bottom surface 2 b. At the corner formed by bottom surface 2 b and the rising portion (sidewall 2 d), a flow velocity of the combustion gas decreases. The drainage water thus stays at the corner. By providing drainage water discharge port 2 aa at this corner, therefore, the drainage water staying at the corner can be effectively discharged through drainage water discharge port 2 aa.

According to the present embodiment, as shown in FIG. 5, the rising portion (sidewall 2 d) is composed of the outer wall of exhaust portion 1. Accordingly, the drainage water staying at a corner between the outer wall and bottom surface 2 b of exhaust portion 1 can be discharged through drainage water discharge port 2 aa.

According to the present embodiment, as shown in FIG. 5, bottom surface 2 b of exhaust portion 1 includes second face 2 bb inclined relative to lower peripheral edge 12 a of secondary heat exchanger case 12 to have a down grade toward first face 2 ba. This facilitates guiding of the drainage water which has fallen to second face 2 bb from the inside of secondary heat exchanger case 12 to first face 2 ba by the inclination of second face 2 bb. Discharge of the drainage water from first face 2 ba through drainage water discharge port 2 aa is thus further facilitated.

If drainage water discharge port 2 aa opens downward, pipe 18 connecting drainage water tank 17 and drainage water discharge port 2 aa shown in FIG. 1 needs to be extended downward. Thus, a space for such downward extension of pipe 18 is needed between drainage water tank 17 and exhaust portion 1, resulting in a corresponding increase in the dimension of combustion apparatus 10 in the up-down direction.

In contrast, according to the present embodiment, as shown in FIG. 1, drainage water discharge port 2 aa is provided in the sidewall of exhaust portion 1 and opens laterally. Thus, pipe 18 connecting drainage water tank 17 and drainage water discharge port 2 aa can be laterally extended for connection to drainage water tank 17. Accordingly, there is no need to provide a space for downward extension of pipe 18 from bottom surface 2 b of exhaust portion 1, allowing for a further corresponding reduction in the dimension of the combustion apparatus in the up-down direction.

According to the present embodiment, as shown in FIGS. 4 and 7, first face 2 ba is provided with guiding inclined face 2 c having a down grade toward drainage water discharge port 2 aa. Discharge of the drainage water on first face 2 ba through drainage water discharge port 2 aa via guiding inclined face 2 c is thus further facilitated.

<Variations>

The embodiment above has described a construction in which drainage water discharge port 2 aa is arranged at the corner formed by bottom surface 2 b and sidewall 2 d, as shown in FIG. 5. The present invention is not limited thereto, however. As shown in FIGS. 9 and 10, drainage water discharge port 2 aa may be arranged at a corner formed by bottom surface 2 b and a plate member 2 g.

Plate member 2 g is a rising portion rising from bottom surface 2 b. Plate member 2 g is arranged in the exhaust path, and does not form the outer wall of exhaust portion 1 (wall facing the outer side of the exhaust path).

Plate member 2 g may be formed integrally with exhaust portion 1 (exhaust collection and guide member 2), or may be prepared separately from exhaust portion 1 (exhaust collection and guide member 2) and then attached to exhaust portion 1 (exhaust collection and guide member 2).

As shown in FIG. 10, plate member 2 g is arranged in region RB where exhaust collection and guide member 2 overlaps with exhaust duct 3 from the point of view as seen in the up-down direction. Drainage water discharge port 2 aa is also arranged in region RB where exhaust collection and guide member 2 overlaps with exhaust duct 3 from the point of view as seen in the up-down direction. Drainage water discharge port 2 aa may be provided in sidewall 2 d and open laterally. Drainage water discharge port 2 aa may open downward at bottom surface 2 b as indicated by a broken line in FIG. 9.

That drainage water discharge port 2 aa is arranged at the corner formed by bottom surface 2 b and a plate member 2 g includes, similarly to the above, not only the case in which drainage water discharge port 2 aa is provided in contact with the corner, but also the case in which drainage water discharge port 2 aa is provided while being laterally spaced apart from the corner by a predetermined dimension. This predetermined dimension refers to a dimension required based on constraints on integral formation of drainage water discharge port 2 aa and plate member 2 g, which is several mm (not more than 1 cm), for example.

At such corner formed by plate member 2 g and bottom surface 2 b, too, a flow velocity of the combustion gas decreases, causing the drainage water to stay. By providing drainage water discharge port 2 aa at this corner, therefore, the drainage water staying at the corner formed by plate member 2 g and bottom surface 2 b can be effectively discharged through drainage water discharge port 2 aa.

As shown in FIG. 11, shielding portions 2 e may rise from bottom surface 2 b into the exhaust path, and drainage water discharge port 2 aa may be arranged in a region

RC opposite to region RA with respect to shielding portions 2 e from the point of view as seen in the up-down direction. Shielding portions 2 e may be attachment portions for bolts, for example, for fixing exhaust collection and guide member 2 to secondary heat exchanger case 12.

In region RC, the flow of the combustion gas is inhibited by shielding portions 2 e, causing a flow velocity of the combustion gas to decrease and the drainage water to stay. That is, in region RC, the flow of the exhausted combustion gas creates a stagnation region of the drainage water, and this causes the drainage water to stay. By providing drainage water discharge port 2 aa in region RC, therefore, the staying drainage water can be efficiently discharged through drainage water discharge port 2 aa.

With drainage water discharge port 2 aa provided in a portion where a flow velocity of the combustion gas decreases and the drainage water stagnation region is created as described above, discharge of the drainage water through drainage water discharge port 2 aa is facilitated.

Drainage water discharge port 2 aa may be provided in sidewall 2 d in region RC and open laterally. In this case, drainage water discharge port 2 aa is provided in sidewall 2 d located opposite to region RA with respect to region RB from the point of view as seen in the up-down direction. Drainage water discharge port 2 aa extends laterally along a direction in which region RA and region RB are aligned with each other. Drainage water discharge port 2 aa may be provided downward in bottom surface 2 b in region RC as indicated by a broken line in FIG. 11.

In the construction shown in FIG. 4, drainage water discharge port 2 aa is provided in sidewall 2 d located in a direction intersecting (for example, orthogonal to) the direction in which region RA and region RB are aligned with each other with respect to region RB. Drainage water discharge port 2 aa shown in FIG. 4 may be provided, similarly to drainage water discharge port 2 aa shown in FIG. 10, in sidewall 2 d located opposite to region RA with respect to region RB. In this case, drainage water discharge port 2 aa extends laterally along the direction in which region RA and region RB are aligned with each other.

While the embodiment above has described combustion apparatus 10 of inverse combustion type as shown in FIG. 1, the present invention may be applied to combustion apparatus 10 of normal combustion type shown in FIG. 12.

As shown in FIG. 12, combustion apparatus 10 of normal combustion type includes, in order from the bottom, fan 16, combustion portion 15, primary heat exchanger 13, secondary heat exchanger 11, and exhaust portion 1.

Combustion portion 15 is a combustion device of normal combustion type which supplies combustion gas upward. Primary heat exchanger 13 is accommodated in primary heat exchanger case 14. Secondary heat exchanger 11 is accommodated in secondary heat exchanger case 12.

Secondary heat exchanger case 12 has lower peripheral edge 12 a and upper peripheral edge 12 b. Exhaust portion 1 is connected to upper peripheral edge 12 b of secondary heat exchanger case 12. Exhaust portion 1 includes exhaust collection and guide member 2, exhaust duct 3, and exhaust vent 4. Exhaust collection and guide member 2 is connected to upper peripheral edge 12 b of secondary heat exchanger case 12. Exhaust vent 4 exhausts combustion gas which has passed through secondary heat exchanger case 12.

Exhaust collection and guide member 2 of exhaust portion 1 has bottom surface 2 b. Bottom surface 2 b has a portion which is located, to avoid the region overlapping with secondary heat exchanger case 12 from the point of view as seen in the up-down direction, in the exhaust path toward exhaust vent 4.

Bottom surface 2 b has first face 2 ba and second face 2 bb. First face 2 ba is parallel to upper peripheral edge 12 b of secondary heat exchanger case 12. Second face 2 bb is inclined relative to upper peripheral edge 12 b of secondary heat exchanger case 12.

Drainage water discharge port 2 aa is provided, to avoid the region overlapping with secondary heat exchanger case 12 from the point of view as seen in the up-down direction, in the exhaust path toward exhaust vent 4. Sidewall 2 d rises from bottom surface 2 b toward exhaust vent 4. Drainage water discharge port 2 aa is provided at a corner formed by bottom surface 2 b and sidewall 2 d.

In combustion apparatus 10 of normal combustion type as described above, too, drainage water can be efficiently discharged through drainage water discharge port 2 aa.

Although the embodiment of the present invention has been described, it should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the meaning and scope equivalent to the terms of the claims. 

What is claimed is:
 1. A combustion apparatus comprising: a combustion portion configured to generate combustion gas; a heat exchanger of latent heat recovery type configured to exchange heat with combustion gas generated by the combustion portion; a heat exchanger case having an internal space and configured to accommodate the heat exchanger in the internal space; an exhaust portion connected to a peripheral edge which is one of an upper peripheral edge and a lower peripheral edge of the heat exchanger case, having an exhaust vent configured to exhaust combustion gas which has passed through the heat exchanger case, and having a bottom surface including a first face parallel to the peripheral edge; and a drainage water discharge port configured to discharge drainage water from the first face of the bottom surface, the drainage water discharge port being provided, to avoid a region overlapping with the heat exchanger case from a point of view as seen in an up-down direction, in an exhaust path from the heat exchanger case toward the exhaust vent.
 2. The combustion apparatus according to claim 1, wherein the exhaust portion has a rising portion rising from the bottom surface, and the drainage water discharge port is arranged at a corner formed by the bottom surface and the rising portion.
 3. The combustion apparatus according to claim 2, wherein the rising portion is composed of an outer wall of the exhaust portion.
 4. The combustion apparatus according to claim 2, wherein the rising portion is a plate member arranged in the exhaust path.
 5. The combustion apparatus according to claim 1, wherein the bottom surface of the exhaust portion includes a second face inclined relative to the peripheral edge of the heat exchanger case to have a down grade toward the first face.
 6. The combustion apparatus according to claim 1, wherein the drainage water discharge port is provided in a sidewall of the exhaust portion and opens laterally.
 7. The combustion apparatus according to claim 6, wherein the first face is provided with a guiding inclined face having a down grade toward the drainage water discharge port. 